High pressure washing devices, commonly referred to as pressure washers, deliver a fluid, typically water, under high pressure to a surface to be cleaned, stripped or prepared for other treatment. High pressure washing devices commonly employ an internal combustion engine or an electric motor that drives a pump that feeds a high-pressure spray wand via a length of hose. A garden hose, or other source of water, is connected to the pump inlet. The high-pressure hose and the spray wand or other tools are connected to the pump outlet.
Typically, pressure washers utilize a piston pump having one or more reciprocating pistons for delivering liquid under pressure to the high-pressure spray wand. The use of two or more pistons generally provides a more continuous spray, higher flow rate and greater efficiency. FIG. 1 provides a diagram of a known oil-less pump 1 that can be used in various suitable commercially available pressure washers and attached to various motors. The pump 1 includes a drive mechanism 2 that uses steel bands 3 to convert a rotary motion from a motor that rotates the drive mechanism 2. The drive mechanism 2 pulls on each of steel bands 3 at predetermined rotational intervals to impart a reciprocal linear motion that activates the pistons 4 in a piston assembly 5.
The pump 1 can experience excessive stresses on many components due to, for example, the rigidity of the steel bands 3 and certain production tolerances. In addition, the drive mechanism 2 can be complex and the pump 1 can experience loss of efficiency due to degrading seals that can be caused by twisting of the valve assemblies 6 during operation of the pump 1.